@article{M2AN_1999__33_3_479_0,
     author = {Kangro, Urve and Nicolaides, Roy},
     title = {Divergence boundary conditions for vector {Helmholtz} equations with divergence constraints},
     journal = {ESAIM: Mod\'elisation math\'ematique et analyse num\'erique},
     pages = {479--492},
     publisher = {EDP-Sciences},
     volume = {33},
     number = {3},
     year = {1999},
     mrnumber = {1713234},
     zbl = {0947.35048},
     language = {en},
     url = {http://www.numdam.org/item/M2AN_1999__33_3_479_0/}
}